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Motors only run for a half second?

#1
I just built the FT Sea Duck. I have all the electronics installed and I have my radio configured exactly per the FT video "HOW TO : Differential Thrust". The servo indicator shows the mixes working properly. However, when I raise the throttle, the motor only runs for less than a half second, then stops. I also did an ESC calibration which seem to work well (all the beeps were correct). It happens with both motors/ESC, either independently, or together. I have checked the battery, and in fact have tried several different batteries.

Transmitter = Graupner MZ-18
Receiver = Graupner GR-24
Battery = Lumineer 4Cell, 35c, 2200 mAh, fully charged
ESC = BL Heli 30A (two of them)
Transmitter configured exactly per https://www.youtube.com/watch?v=JsMHBxKbGJU

Any Idea where the problem is? What is the fix?

Thanks!
 
Last edited:

PsyBorg

Wake up! Time to fly!
Mentor
#2
If that 4c listed on your battery is correct that would be the reason. That's not enough oomph to light a few led's for a minute let alone turn two motors.

Did you check the batteries before and after these attempts to see what the charge is and how much it changes? It almost sounds like they are in low voltage cutoff from the start.
 

Montiey

Master Tinkerer
#3
4c seems amazingly low, I'd be surprised if a 2200 pack was anything less than 10c. Anyhow, yeah. You'd only be able to put about 10 amps on that battery before the voltage sag is too much to run the motors. Do you think you can attach a volt meter to the power lines to monitor the voltage? That way we'd know that it's a voltage sag problem.
 
#4
Hmmm, I would think that he meant to say 4S instead of 4C, just to clarify for the OP, "S" means cells and "C" generally stands for discharge rate.
 

Montiey

Master Tinkerer
#5
4s 2200. Hmm. Something's wrong here, but I don't think it's the battery unless it IS a 4C pack. I would start by testing one motor, with one ESC on an unmixed channel on the receiver (even better, a servo tester if you have one). It could be something to do with the mixing, not sure.

GL! :)
 

Hai-Lee

Old and Bold RC PILOT
Mentor
#7
It definitely sounds like a battery voltage sag issue. If the battery is fine then one of your connections to the battery is dodgy.

Do the ESCs reboot after they have shut down? Try disconnecting one motor at a time and see if the remaining, (still connected), motor behaves properly if it does then a brownout is suspected. Try both motors individually and if the problem is the same for each motor individually you may need to access the programming of the ESCs and ensure that they are not programmed for a higher cell count i.e. 6 cell and they are suffering low voltage cutout when you draw power from the battery because they are expecting a far higher operating voltage. They could be programmed for 22.2 and you are trying to operate them on 14.8.

Just a thought!
 
#8
UPDATE:
I tested each part independently (motor, ESC, battery, receiver, wiring harness, etc.) I used part from my other FT aircraft (FT Spear, FT Mustang, & FT Duster) to interchange with my Sea Duck parts. Per the advice above I also tested the voltage, with no significant sag.
RESULTS:
The ESCs, (yes, BOTH!) Were causing the problem. These were new ESCs and were evidently bad out-of-the-box. I have contacted FT support and hope they will send replacements.